In addition to implantable pacemaker arrangements, which deliver stimulation pulses to a patient's heart over endocardial electrode lines with distal electrodes, similarly constructed implanted cardioverters or defibrillators have also long been known. These have the important advantage of automatic startup through internal detection of life-threatening cardiac states of the patient, similarly to external defibrillators, which are used by medical personnel when a patient's heart stops. They may thus intervene in a case of ventricular fibrillation or cardiac arrest in a patient with practically no delay and independently of the presence of assistants.
On the other hand, the success rate of implantable cardioverters and/or defibrillators is significantly lower than that of external defibrillators. This is due, firstly, to the limited energy storage capacity of implantable devices with a battery power supply and, secondly, to the restrictions imposed on the electrode line, laid endocardially or epicardially, with regard to the influence of the electric energy of the shock pulses on myocardial tissue.
In addition, today's implantable cardioversion (ICD) systems can be therapeutically successful only when the cause of the ventricular fibrillation (VF) is due strictly to rhythmogenic factors or a temporary disturbance in myocardial profusion. However, sole defibrillation of a VF as part of an acute myocardial infarction tends to have a poor prognosis because after defibrillation, the conditions for renewed VF then still exist unchanged.
Therefore, increasing the defibrillation efficiency has been formulated in expert committees as being an important concern of future ICD therapies. Current ICD systems are fully developed for the most part with regard to the electric therapy and offer only a slight potential for the desired increase in defibrillation efficiency. The anticipated improvements have been very difficult or impossible to detect because of the number of patients required for clinical studies.
In this context, it is noteworthy that in external defibrillation in the context of reanimation, drug therapies are always used in addition to defibrillation, to thereby increase the defibrillation efficiency (see, e.g., http//www.inm-online.de/pdf/Wissen/Reanimation/algorithmus 2005.pdf).
Implantable arrangements for metered delivery of drugs, e.g., in the form of implantable insulin pumps, have long been known and are also in use to a certain extent. Such arrangements have also been the object of intense development efforts in recent years.
For example, EP 1 210 064 B1 presents and claims a thermally activatable microchip as a delivery device for chemicals, in particular drugs, in which the release of the drug from a depot is triggered essentially by resistance heating and subsequent destruction of a cap on the depot. WO 2004/071487 A2 also describes an arrangement for controlled drug delivery, in which a plurality of individual depots is arranged on a substrate, each being openable by electric control to release the quantity of drug contained therein. This also describes how such drug depots are arranged on the distal end of a catheter and are connected to an implantable control unit.
WO 2004/033034 A1 describes a medical device for neural stimulation and controlled drug delivery, also comprising a microchip for drug delivery in addition to an implantable electrode line. The microchip having a plurality of individually controllable drug depots is placed on a device housing which holds a control unit for drug delivery or a joint control unit for drug delivery and electric neural stimulation. WO 2004/033036 A2 describes an arrangement that is very similar but is designed for coordinated drug delivery and cardiac monitoring and/or stimulation. In one embodiment, the arrangement described here also has cardioversion electrodes on corresponding electrode lines, and the drug may also be released from the depots on the device housing with a certain interval of time before delivery of a cardioversion shock pulse.
US 2006/0041276 A1 describes a method and an arrangement for providing combined electrotherapy and drug therapy, which are provided for regulating the cardiac rhythm in particular. In various embodiments, the arrangement comprises an implantable electrostimulation device and implantable drug delivery device combined with a shared electrode catheter or two separate electrode lines and/or infusion lines or an electrostimulation and drug delivery device combined in a single housing and having separate control units or just one shared control unit and a single electrode and drug delivery catheter. It is also described that the implantable medical device may have a cardioversion and/or defibrillation unit and the electrode line and/or the catheter may have shock electrodes.
The approaches known for coordinated electrostimulation (in particular cardioversion/defibrillation) and drug delivery are relatively complex to implement, and are not readily compatible with established ICD approaches.